In recent years and continuing, optical interconnections likely to provide wideband inter-chip communications at low power-consumption have been attracting attention in the technologies of supercomputers or servers.
In supercomputers or servers, multiple boards are connected to a backplane board and a large-scale integration (LSI) chip is mounted on each board to carry out computation. With optical interconnections, electrical signals generated by the LSI chip are converted into optical signals by an electrical-to-optical converter on the board. The optical signals are transmitted to another board and converted into electrical signals before they are input to the LSI chip. Optical transmission paths are arranged on or inside the backplane board. Optical transmission paths are also arranged on each board, extending from the board edge to the optical-to-electrical converter and the electrical-to-optical converter. The boards are each connected to the backplane board using optical connectors.
Optical connectors for use in connection with the backplane board are generally placed at the board edges. In general, multifiber optical connectors are used and an attachable and detachable structure is employed from the viewpoint of the system configuration and system maintenance. In an optical connector, an optical transmission line is held by a ferrule with a high degree of accuracy and housed in a connector housing. The ferrule is mated with a counterpart ferrule in the connector housing.
For optical connectors, cost redaction, as well as quality improvement, is desired. To reduce manufacturing cost, unpolished fibers with their tips unpolished have promise. A connector structure enabling to achieve accurate optical connection between unpolished fibers is known. See, for example, Japanese Laid-open Patent Publication No. 2012-194481. This connector structure makes use of deformation of the ferrule and bending or buckling of optical fibers, and achieves low-loss connection between multifiber connectors, each having uneven fiber lengths.
However, with the conventional structure making use of ferrule deformation and fiber buckling, undesirable external forces such as shaking or impingement may be applied to the bending optical fibers during connection of the ferrules inside the connector housing. If an external force acts in the direction of the ferrule insertion (parallel to the light propagation axis of an optical fiber), buckling exceeding a specified level occurs at the optical fibers. If an external force acts in the direction of the fiber alignment (orthogonal to the light propagation axis of the optical fiber), the bending fibers are subjected to excessive stress and optical fibers may be damaged.
It is desired for an optical connector to prevent an excessive amount of buckling or stress from being generated in optical fibers over a specified level to avoid damage to the optical fibers.